Resources

Forms:

Denver-Area Music Stores for piano books & sheet music:

Music Theory and Games:

Music Theory Pro - this app allow you to quiz yourself on everything from note identification and key signatures to scales, chords, and intervals, and it includes a very helpful ear training section. Recommended for intermediate to advanced learners. It helps to get some hands-on practice with this in guided lessons first!
Chord Inversion Exercises
Note Reading Worksheets
Consider purchasing Harmonic Vision Music Ace software for your children's use at home! This package of lessons is comprehensive, fun, and available for around $40 at Sweetwater.com, Westmusic.com, Amazon.com, or your local music stores.

Metronome:

Articles and Reference:

Dallas Symphony Orchestra Article with Great Practice Tips for Kids!
This page can help you identify notes on the piano & treble cleff staff: http://www.emusictheory.com/explore/noteNames.html
You can click a note on the keyboard to see where it’s played on the piano and what it sounds like: http://www.emusictheory.com/explore/pianoKeys.html
Once you know the note names on the staff, you can use this page to drill yourself: http://www.emusictheory.com/practice/noteNames.html
FUN! Click on this grid to explore different melody, rhythm and harmony patterns, and it immediately plays back the sequences you create: http://tonematrix.audiotool.com/
Good music fundamentals for older kids who can read text on their own: http://www.sfskids.org/

Adults and intermediate to advanced players may enjoy these brief online tutorials on a variety of music theory topics for the keyboard: http://www.musictheoryminute.com/

Other Sources for Great Music Teachers in NE Denver: